DESCRIPTION: (Applicant's Description) Breast Cancer Risk: Residential Environment and Genetics There is evidence that environmental factors related to industrialization may be important in breast cancer etiology. There has been little study of proximity to potentially toxic industrial sites as breast cancer risk factors. We propose to conduct a case-control study to examine location of residence during adult life in relation to breast cancer risk. The aims of the study are: 1) To investigate distance from steel mills, chemical factories, and other industrial sites of the residence as risk factors. The time periods to be examined will be (1 ) the primary residence during the period between menarche and first pregnancy (if any, otherwise menopause) and (2) residence (s) 10 and 20 years ago; 2) To examine estimated exposure to benzene and to PAHs based on residential exposure during these time periods as risk factors. Secondary objectives are: 3) To examine genetic variability in metabolism by NQ01, GST M1-1 , GST P1-1 and CYP 1A1 in relation to these exposures and breast cancer risk; 4) To evaluate all adult residences in relation to distance from potentially important exposures (steel mills, chemical factories, etc.) and risk; 5) To examine estimated exposure to benzene and to PAHs during the entire adult life and risk. We will use data from an ongoing case-control study of breast cancer in Erie and Niagara Counties including approximately 1000 cases of incident, primary, histologically-confirmed breast cancer and more than 2000 controls, age 35-79, frequency-matched to cases. About 75 percents of participants in the original study lived in these counties at the time of their menarche. Addresses for the women at the time of their birth and at menarche will be geocoded using a Geographic Information System (GIS). Historical data will be collected regarding location of potentially important industrial sites. We will calculate odds ratios and 95 percents confidence intervals for distance from each category of potential exposure and for an index of probable level of exposure to PAHs and to benzene and we will examine risk within categories stratified on genotype. This is a unique and cost effective opportunity to examine a hypothesis of potentially great public health importance in a relatively residentially stable population.